Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended				3 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Divestiture Transaction	Jun. 30, 2012 Federal	Dec. 31, 2012 Federal
Income Tax Disclosure
Effective income tax rate	42.60%	39.00%	42.50%	33.80%
Federal income tax refund received							$ 59,900,000	$ 71,400,000
Current tax liability	$ 190,836,000		$ 190,836,000		$ 48,237,000	$ 128,900,000